There are conventionally known rolling mills that cast molten metal between casting rolls installed in a casting device to form a plate-like slab, and further shape the slab by rolling it between finishing milling rolls.
In such rolling mills, there are cases where, when the molten metal is cast between the casting rolls, a thickness variation is produced in the slab at its edge portions in its width direction due to thermal deformation or the like of the casting rolls, resulting in a so-called edge drop or edge up.
For example, in the case where a slab with such an edge drop or edge up is rolled between a pair of rolls whose peripheral surface has a linear contour shape, a pressure difference is produced between the rolling reduction force acting on the central portion of the slab in its width direction and the rolling reduction force acting on its edge portions. This leads to a non-uniform rolling reduction in the width direction of the slab. As a result, a difference in the extension ratio is produced between the central portion and the edge portions, leading to a defective shape such as corrugation in a slab shape.
Therefore, Patent Document 1 discloses a rolling mill in which a contour shape of a peripheral surface of both finishing milling rolls is configured to have edge portions with an inclination angle steeper with respect to the axis direction than that of a central portion.
According to such a rolling mill as disclosed in Patent Document 1, a movement device is used to move one finishing milling roll and the other finishing milling roll in directions opposite to each other along the axis direction, making it possible to change the distance between the facing edge portions of the work rolls. Therefore, a thickness variation in the edge portions in the width direction of the slab that is cast between the casting rolls is measured, and the movement device is used to move the finishing milling rolls over time based on the measurement result, to thereby render it possible to always make uniform the rolling reduction in the width direction of the slab by the finishing milling rolls.
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2002-11503